smp: Rename flush_smp_call_function_from_idle()

This is invoked from the stopper thread too, which is definitely not idle.
Rename it to flush_smp_call_function_queue() and fixup the callers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220413133024.305001096@linutronix.de

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e644578..07bacb0 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2411,7 +2411,7 @@ static int migration_cpu_stop(void *data)
         * __migrate_task() such that we will not miss enforcing cpus_ptr
         * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
         */
-       flush_smp_call_function_from_idle();
+       flush_smp_call_function_queue();
 
        raw_spin_lock(&p->pi_lock);
        rq_lock(rq, &rf);

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 8f8b502..60295db 100644 (file)
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -327,7 +327,7 @@ static void do_idle(void)
         * RCU relies on this call to be done outside of an RCU read-side
         * critical section.
         */
-       flush_smp_call_function_from_idle();
+       flush_smp_call_function_queue();
        schedule_idle();
 
        if (unlikely(klp_patch_pending(current)))

diff --git a/kernel/sched/smp.h b/kernel/sched/smp.h
index 5719bf9..2eb23dd 100644 (file)
--- a/kernel/sched/smp.h
+++ b/kernel/sched/smp.h
@@ -9,7 +9,7 @@ extern void sched_ttwu_pending(void *arg);
 extern void send_call_function_single_ipi(int cpu);
 
 #ifdef CONFIG_SMP
-extern void flush_smp_call_function_from_idle(void);
+extern void flush_smp_call_function_queue(void);
 #else
-static inline void flush_smp_call_function_from_idle(void) { }
+static inline void flush_smp_call_function_queue(void) { }
 #endif

diff --git a/kernel/smp.c b/kernel/smp.c
index 01a7c17..8e85f22 100644 (file)
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -96,7 +96,7 @@ static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data);
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
 
-static void flush_smp_call_function_queue(bool warn_cpu_offline);
+static void __flush_smp_call_function_queue(bool warn_cpu_offline);
 
 int smpcfd_prepare_cpu(unsigned int cpu)
 {
@@ -141,7 +141,7 @@ int smpcfd_dying_cpu(unsigned int cpu)
         * ensure that the outgoing CPU doesn't go offline with work
         * still pending.
         */
-       flush_smp_call_function_queue(false);
+       __flush_smp_call_function_queue(false);
        irq_work_run();
        return 0;
 }
@@ -541,11 +541,11 @@ void generic_smp_call_function_single_interrupt(void)
 {
        cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->gotipi, CFD_SEQ_NOCPU,
                      smp_processor_id(), CFD_SEQ_GOTIPI);
-       flush_smp_call_function_queue(true);
+       __flush_smp_call_function_queue(true);
 }
 
 /**
- * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
+ * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks
  *
  * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an
  *                   offline CPU. Skip this check if set to 'false'.
@@ -558,7 +558,7 @@ void generic_smp_call_function_single_interrupt(void)
  * Loop through the call_single_queue and run all the queued callbacks.
  * Must be called with interrupts disabled.
  */
-static void flush_smp_call_function_queue(bool warn_cpu_offline)
+static void __flush_smp_call_function_queue(bool warn_cpu_offline)
 {
        call_single_data_t *csd, *csd_next;
        struct llist_node *entry, *prev;
@@ -681,7 +681,20 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
                      smp_processor_id(), CFD_SEQ_HDLEND);
 }
 
-void flush_smp_call_function_from_idle(void)
+
+/**
+ * flush_smp_call_function_queue - Flush pending smp-call-function callbacks
+ *                                from task context (idle, migration thread)
+ *
+ * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it
+ * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by
+ * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to
+ * handle queued SMP function calls before scheduling.
+ *
+ * The migration thread has to ensure that an eventually pending wakeup has
+ * been handled before it migrates a task.
+ */
+void flush_smp_call_function_queue(void)
 {
        unsigned long flags;
 
@@ -691,7 +704,7 @@ void flush_smp_call_function_from_idle(void)
        cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->idle, CFD_SEQ_NOCPU,
                      smp_processor_id(), CFD_SEQ_IDLE);
        local_irq_save(flags);
-       flush_smp_call_function_queue(true);
+       __flush_smp_call_function_queue(true);
        if (local_softirq_pending())
                do_softirq();